The present invention relates to a method of producing a pocket opening having a flap, a piping strip, and a pocket bag on an automatic sewing machine, and a device for carrying out this method.
The assignee Durkoppwerke GmbH manufactures a sewing machine under the name Durkopp 745 by means of which pocket openings having flaps can be produced automatically.
For this purpose, the workpiece which is to be provided with the pocket opening, for instance the front part of a jacket or trousers, or a part of a coat, is aligned on the work plate which is located in front (that is, in advance) of the sewing region. Above this there is arranged, on the one side, a flap-application and transfer device such as is known, for instance, from Federal Republic of Germany OS 26 56 720, equivalent to U.S. Pat. No. 4,281,606 and, on the other side, an application device for the piping strip and the pocket bag. The disclosures of this document and all other prior art materials cited herein are expressly incorporated by reference. The piping strip and the pocket bag are inserted into the appropriate application device and aligned, and the flap is inserted into the application device. The piping strip, pocket bag and flap are lowered onto the workpiece, and fixed there by means of the sewing-material clamp, whereupon all parts are transported into the sewing region.
The length of the applied flap is detected by an optical sensor which is functionally connected with the control of the sewing machine and the formation of the seam is so controlled that the seam extends precisely over the entire length of the flap. After the piping strip and the pocket bag are sewed together to the workpiece, on the one hand, and after the flap, piping strip and workpiece are sewed together on the other hand, the pocket opening is cut in known manner (Federal Republic of Germany OS 34 04 758, equivalent to U.S. Pat. No. 4,589,358).
In the case of a pocket opening produced by this method, the free end of the pocket bag which is connected to the piping strip must then be sewn to the flap in order to close the pocket bag, which requires a relatively complicated operation.
According to another method, it is also known to place half of a pocket bag on the flap and half on the piping strip, sew them together to the workpiece and then close the two pocket bag halves in simple manner to each other, for instance by an overcast stitch. Since the flap is covered in this way by the half of the pocket bag which rests on it, the length of the flap cannot be detected by an optical sensor after it is transported into the sewing region, so that it is necessary to work with a constant seam length. There is the disadvantage here that, as a result of manufacturing tolerances, the prefabricated flaps differ in length from one another, so the proper formation of the seam does not always take place.